Numerous insects are serious pests of common agricultural crops. One method of controlling insects has been to apply insecticidal organic or semiorganic chemicals to crops. This method has numerous, art-recognized problems. A more recent method of control of insect pests has been the use of biological control organisms which are typically natural predators of the troublesome insects. These include other insects, fungi (milky-spore) and bacteria (Bacillus thuringiensis cv., commonly referred to as "Bt"). However, it is difficult to apply biological control organisms to large areas, and even more difficult to cause those living organisms to remain in the treated area for an extended period. Still more recently, techniques in recombinant DNA have provided the opportunity to insert into plant cells cloned genes which express insecticidal toxins derived from biological control organisms such as Bt. This technology has given rise to additional concerns about eventual insect resistance to well-known, naturally occurring insect toxins, particularly in the face of heavy selection pressure, which may occur in some areas. Thus, a continuing need exists to identify naturally occurring insecticidal toxins which can be formed by plant cells directly by translation of a single structural gene.
European Patent Application 204,590, based upon U.S. patent application Ser. No. 725,368, describes a method of genetically modifying a plant cell to control expression of heterologous foreign structure genes, including a lectin from Phaseolus vulgaris. In the method, the plant cell is transformed to contain a pRi T-DNA promoter and a heterologous foreign structural gene, the promoter and the structural gene being in such position and orientation with respect to one another that the structural gene is expressible in a plant cell under control of the promoter.
Likewise, European Patent Application 186,425, based upon U.S. patent application Ser. No. 685,824, describes a recombinant DNA expression vector which comprises (a) a transcription unit, flanked by T-DNA border sequences, which comprises a promoter and associated amino terminal region encoding sequences and a terminator signal sequence in which the sequences are derived from one or more genes which are naturally expressed in a plant cell, and (b) an antibiotic resistance gene-encoding sequence located between the promoter and associated amino-terminal region-encoding sequence and the terminator sequence and (c) a DNA fragment containing a replicon that is functional in Agrobacterium.
PCT application 8807087, based upon U.S. patent application Ser. No. 168,109, discloses a recombinant virus expression system comprising a Heliothis polyhedrin promoter and a nucleotide sequence encoding a heterologous peptide or protein, which may have insecticidal activity.
European patent application publication number 351,924, published Jan. 24, 1990, describes a transgenic plant such as tobacco or potato comprising a lectin gene expressing a lectin within the plant foreign to the plant as found in nature. Concanavalin A, lentil (Lens culinaris) lectin, favin (Vicia faba lectin) and pea lectin are specifically disclosed. As can be seen from the data herein, lens culinaris lectin has been tested and found ineffective under the criteria employed here. Likewise, at least one of the lectins employed herein is disclosed as being produced in an insect cell/baculovirus expression system, as disclosed in PCT patent application 89-01037, based upon U.S. patent application Ser. No. 153778, which makes its potent insecticidal activity surprising.
European Patent Application publication number 237,676, based on U.S. application Ser. No. 837,583, describes a recombinant DNA sequence which codes for any of a) ricin A chain protein; b) the B chain portion of the ricin precursor protein; c) the A chain and B chain portions of the ricin precursor protein; or d) ricin precursor protein or polypeptide. An expression system is described as including one of the foregoing DNA sequences operably linked to a control sequence compatible with a recombinant host cell. The objective is to produce ricin toxin, precursor or fragments thereof in commercial quantities.
European Patent Application 204,590, based on U.S. patent application Ser. No. 725,368, relates to a method of genetically modifying a plant cell with a pRi tDNA promoter and a heterologous foreign structural gene, such as the lectin from Phaseolus vulgaris. The heterologous foreign structural gene is in position and orientation with respect to the promoter such that the structural gene is expressible in a plant cell under the control of the promoter. Expression of the Phaseolus vulgaris lectin is stated to be useful in improving the nutritional quality of the plant cell proteins.